In the combustion process of a gas turbine engine, nitrogen oxides and other types of regulated emissions are produced. Specifically, a simple cycle gas turbine emits hot flue gases that contain unacceptable levels of nitrogen oxides. One solution for reducing the overall levels of nitrogen oxide emissions is the use of a selective catalyst reduction system. Generally described, the selective catalyst reduction system adds a reductant, typically ammonia or urea, to the hot combustion gas stream before passing the combustion gas stream through a catalyst bed so as to absorb selectively the nitrogen oxides and the reducing agent. The absorbed components undergo a chemical reaction on the catalyst surface and the reaction products are desorbed. Specifically, the reactant reacts with the nitrogen oxides in the combustion gas stream to form water and nitrogen. Other types of catalysts and other types of reductants may be used.
The overall efficiency of the selective catalyst reduction system may depend at least in part on the temperature of the hot combustion gas stream. Specifically, the efficient temperature range of the selective catalyst reduction system may be relatively narrow. As such, the hot combustion gas stream generally should be sufficiently cooled before reaching the catalyst bed. Moreover, careful metering and distribution of the reductant to the combustion gas stream upstream of the catalyst bed may be required for the selective catalyst reduction system to convert and remove a sufficient level of the nitrogen oxides.
Mobile, simple cycle combustion turbine-generators may be delivered and operated at remote locations with immediately power needs. These combustion turbine-generators may require emission control systems to minimize nitrogen oxide emissions from the combustion turbine so as to meet applicable emission requirements. The exhaust gas quality and the overall design of the exhaust systems in these simple cycle combustion turbines, however, may not be suitable for treatment by known types of selective catalyst reduction technology. Specifically, selective catalyst reduction technology generally may be applied to simple cycle turbine exhaust after cooling treatments also have been applied. Selective catalyst reduction technology also may require ammonia reagent delivery systems and catalyst layers. The common delivery of a selective catalyst reduction system thus generally requires substantial erection, assembly, and other basic construction activities at the final turbine-generator location. Often, there may be limited skilled labor available at the remote location to perform the construction and it may be expensive to bring sufficient skilled labor to such a remote location. The design and construction methods used for these common selective catalyst reduction systems thus may make them substantially unsuitable for transport.